$ cd /var
$ pwd
/var

↓はカレントディレクトリ（/var）内表示。
$ ls
account  crash  gdm       local           mail      run           var
adm      cvs    gitrepos  lock            nis       run.runmove~  www
backups  db     gopher    lock.lockmove~  nmbd      sharedata     yp
cache    empty  kerberos  log             opt       spool
chef     games  lib       lost+found      preserve  tmp
$ ls .
account  crash  gdm       local           mail      run           var
adm      cvs    gitrepos  lock            nis       run.runmove~  www
backups  db     gopher    lock.lockmove~  nmbd      sharedata     yp
cache    empty  kerberos  log             opt       spool
chef     games  lib       lost+found      preserve  tmp
 ls ./
account  crash  gdm       local           mail      run           var
adm      cvs    gitrepos  lock            nis       run.runmove~  www
backups  db     gopher    lock.lockmove~  nmbd      sharedata     yp
cache    empty  kerberos  log             opt       spool
chef     games  lib       lost+found      preserve  tmp


↓は一つ上、つまり/の中身表示
$ ls ..
bin   dev  home        lib    lost+found  mnt  proc  run   srv  tmp  var
$ ls ../
bin   dev  home        lib    lost+found  mnt  proc  run   srv  tmp  var
boot  etc  initrd.img  lib64  media       opt  root  sbin  sys  usr  vmlinuz